Sovtek is a brand of vacuum tube owned by Mike Matthews's New Sensor Corporation and manufactured in Saratov, Russia. They are often used in guitar amplification and include versions of the popular 12AX7, EL84, EL34, and 6L6. Many of the vacuum-tube amplifiers in modern production are factory-fitted with Sovtek valves, due to their low noise performance and lower prices than other makes.In the 1990s Sovtek also manufactured tube amplifiers at factories in St.